Abstract Velocity-dependent potentials are investigated in both the Lagrangian and the Hamiltonian formalism in quantum mechanics. In order to achieve a consistent method, a canonical transformation is introduced for the type of Lagrangian 1 2 q ig ij(q) q j − V(q) where g ij and V are functions of position operators q i only. It is found that the proper Hamiltonian satisfying the canonical equation of motion should be H = p iq i − L − Z where Z is a function of q i and is expressed in terms of g ij ( q). This formulation has been examined by some examples. The Euler-Lagrange equation that is consistent with the canonical equation of motion is derived and it turns out to be in an apparently dissipated form. However, the physical system could be a non-dissipative one. Finally, the Schroedinger equation is investigated according to the above argument.